The vapor pressure of pure water and pure ethanol at 2 5 ° � are 2 4 Torr and 4 4 Torr, respectively. Suppose you have a water - ethanol mixture and the total vapor pressure is 3 1 . 2 Torr. Sucrose, � 1 2 � 2 2 � 1 1 , is a non - volatile solute that will not contribute to the total vapor pressure. When 0 . 0 3 moles of sucrose is added to the water - ethanol mixture, the vapor pressure drops to 2 9 . 8 Torr. a ) Write the expression for � t o t a l in terms of mole fractions, � . Rewrite this in terms of moles, � . b ) What quantities remain the same before and after the addition of the sucrose? c ) How many moles of water are present in the solution?